Fan



Jan. 17, 1939.

E. W. DENMAN FAN Filed Oct. 9, 1936 WITNESSES Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE A FAN Earl W. Denman, Longmeadow, Mass, assignor to Westinghouse of Pennsylvania Electric & Manufacturing Company, East Pittsburgh, Pa.,

a corporation Application October 9, 1936, Serial No. 104,822

2 Claims.

blade at a smaller angle than the pitch near the hub or center of the fan, so that there will be some compensation for the difference in the peripheral velocities at different radii, thereby tending to give an approximately even axial airvelocity over the entire area of the fan. Variatlons from this optimum condition are considerable, as a result of different designs and shapes of fan blades which have been used. To obtain the best result a warped surface is desirable. This may be obtained relatively easily in metal blades, but to obtain a warped surface with blades such as are made from molded material, the expense would be considerably greater due to the requirement for individually molding each blade, or building up the blades from layers which are pressed and baked.

The object of my invention is to provide a special shape and arrangement of fan blade whereby the blade, whether of metal or of molded material, may be of cylindrical shape, which does not require warping orindividual molding.

A more specific object of my invention is to provide simple and economical means whereby the practical effect of increasing the pitch of the blade near the center of the fan may be obtained in a cylindrically formed blade.

A further object of my invention is to provide a substantially rectangularly, shaped blade, with rounded corners, made from cylindrical material with the straight-line generatrices of the cylinder disposed at an angle to the sides. The angular disposition effects the desired change in pitch from the hub to the periphery, and the approximately rectangular configuration also serves to reduce waste in cutting a number of blades from a single cylinder ofmaterial.

With the foregoing and other objects in view, my invention consists in the shapes, structures, combinations and methods hereinafter described and claimed and illustrated in the accompanying drawing, wherein a Figure 1 is a front elevational view of a fan embodying my invention,

Fig. 2 is a side view thereof, and

Fig. 3 is a cross sectional view through one of the blades, on the plane indicated by the line III-III in Fig. 1.

I have illustrated my invention in a fan utilizing four blades 4 which are mounted on a spider 5 carried by a hub 6 which serves to mount the fan on the fan-shaft (not shown). The arms of the spider 5 extend out radially from the hub 6, and are slightly twisted as shown, so as to give the fan blades a small angle of entrance on the leading edge 1, and a greater pitch on the trailing edge 8, the direction of rotation being as shown by the arrow 9 in Fig. 1. Each fan blade is made of substantially cylindrical material, as shown by the cross section in Fig. 3, with the axis of the cylinder substantially parallel to the line of attachment II, that is, substantially parallel to the center line of the spider arm which supports the blade.

It will be noted that the line of attachment ll passes through approximately the center of each blade, that is, the area of the blade material to the right of it is approximately the same as the area of the blade material to the left of it, as viewed in Fig. 1. According to my invention, however, a greater amount of the blade-surface which lies on the leading side 1 of said center line of attachment II is disposed near the periphery of the fan, and a greater amount of the blade-surface which lies on the trailing side 8 of said center line of attachment is disposed near the axis of the fan. The result of this construction is that the entrance pitch at the leading edge, near the periphery of the fan as at [3, that is, where the leading edge I is furthest displaced from the center line H, is very small. The pitch is measured in a plane at right angles to the radius at any point, and is the angle between the blade-surface and the plane of the fan at that point, the plane of the fan being a plane at right angles to the axis of the fan. Near the hub of each blade, as at M, the leading edge 1 comes closer toward the center line of attachment ll, so that the entrance angle or pitch is larger than near the periphery, as at I3. On the other hand, at the trailing side 8 of the fan blade, the cylindrically curved blade extends around a shorter distancefrom the center line at the periphery, than at the hub, so that the final pitch of the fan blade, at the trailing edge of the blade, is slightly greater at the hub than at other points, thereby assisting in equalizing the airvelocities in an axial direction, as indicated by the arrows IS in Fig. 2, so as to make these axial air-velocities more nearly uniform over the entire area of the fan.

It will be noted, from Fig; 1, that the fan blades are of substantially rectangular shape, with rounded corners, thus providing for obtaining ference of a circle, while keeping the successive positions of the generatrix always parallel, it will be noted that one of the positions of the generatrix will pass through the axis of the fan and will coincide with the line of attachment ll, because this line of attachment is substantially radial, or at right angles to the axis of the fan. Thus, by the simple expedient of cutting or forming approximately rectangularly shaped blades on a bias, out of cylindrically shaped material,

and mounting them as hereinbefore shown and described, I have obtained the essential objects of my invention at a very minimum of expense.

I claim as my invention: 1. A multi-blade fan for use in a gaseous medium, characterized by each blade being of sheet-like material in substantially the shape of a portion of a cylinder, with a substantially straight-line generatrix of the cylinder passing through the fan-axis and passing through approximately the center of the blade, with a greater amount of the blade-surface which lies on the leading side of said generatrix disposed near. the periphery of the fan, and with a greater amount of the blade-surface which lies on the trailing side of said generatrix disposed near the axis of the fan.

2. A multi-blade fan for use in a gaseous medium, characterized by each blade being of sheetlike material having'an approximately rectangular shape with rounded corners, each blade having a curvature substantially in accordance with the surface of a cylinder having its straight-line generatrices disposed at an acute angle to the sides of the rectangle, and mounting means for mounting the blades in a twisted position so as to have an entranceangle which is largernear the hub than near the periphery.

EARL W. DENMAN. 

